title: Disruption of a conserved region of Xist exon 1 impairs Xist RNA localisation and X-linked gene silencing during random and imprinted X chromosome inactivation.
abstract: In XX female mammals a single X chromosome is inactivated early in embryonic development, a process that is required to equalise X-linked gene dosage relative to XY males. X inactivation is regulated by a cis-acting master switch, the Xist locus, the product of which is a large non-coding RNA that coats the chromosome from which it is transcribed, triggering recruitment of chromatin modifying factors that establish and maintain gene silencing chromosome wide. Chromosome coating and Xist RNA-mediated silencing remain poorly understood, both at the level of RNA sequence determinants and interacting factors. Here, we describe analysis of a novel targeted mutation, Xist(INV), designed to test the function of a conserved region located in exon 1 of Xist RNA during X inactivation in mouse. We show that Xist(INV) is a strong hypomorphic allele that is appropriately regulated but compromised in its ability to silence X-linked loci in cis. Inheritance of Xist(INV) on the paternal X chromosome results in embryonic lethality due to failure of imprinted X inactivation in extra-embryonic lineages. Female embryos inheriting Xist(INV) on the maternal X chromosome undergo extreme secondary non-random X inactivation, eliminating the majority of cells that express the Xist(INV) allele. Analysis of cells that express Xist(INV) RNA demonstrates reduced association of the mutant RNA to the X chromosome, suggesting that conserved sequences in the inverted region are important for Xist RNA localisation.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford, UK.
authors.forename: Claire E
authors.initials: CE
authors.lastname: Senner
authors.forename: Tatyana B
authors.initials: TB
authors.lastname: Nesterova
authors.forename: Sara
authors.initials: S
authors.lastname: Norton
authors.forename: Hamlata
authors.initials: H
authors.lastname: Dewchand
authors.forename: Jonathan
authors.initials: J
authors.lastname: Godwin
authors.forename: Winifred
authors.initials: W
authors.lastname: Mak
authors.forename: Neil
authors.initials: N
authors.lastname: Brockdorff
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D002478:Cells, Cultured; D005091:Exons / Q000235:genetics*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D050172:Genes, X-Linked / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D051379:Mice; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D049951:X Chromosome Inactivation / Q000235:genetics*
chemical_list: D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; C077885:XIST non-coding RNA